Periodic backwash seawater reverse osmosis desalination apparatus and method

Abstract

The application discloses a periodic back-flushing seawater reverse osmosis desalination device, which comprises a shell, a filter core assembly, a piston assembly, an inclined disc and a driving device. The shell is internally sequentially provided with a seawater layer, a piston layer and a fresh water layer from top to bottom. A plurality of filter core assemblies are arranged in an annular array in the seawater layer. The filter core assembly comprises a filter core inner cylinder and a surface reverse osmosis membrane. The piston assembly is arranged below the filter core assembly in a one-to-one correspondence. An internal passage is arranged in the piston body along an axial direction. An electromagnetic valve for controlling the opening and closing of the internal passage is arranged. An electromagnetic device is arranged on the outer surface of the piston outer cylinder. When the piston body moves to a matching position, the electromagnetic valve is opened to allow fresh water to fall through the internal passage. The lower end of the piston body is arranged in the annular track of the inclined disc. The driving device drives the rotation of the inclined disc. The inclined disc drives the piston body to complete a reciprocating motion once per revolution. The application can complete twice back-flushing and fresh water collection in one cycle, and improve the service efficiency and life of the membrane assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of seawater desalination, in particular to a periodic backwashing seawater reverse osmosis desalination device and method. BACKGROUND

[0002] In recent years, seawater desalination has been highly concerned in the industrial field. The seawater resources in coastal areas are converted into fresh water that can be used by humans to solve the contradiction between water supply and demand. At present, the methods used for seawater desalination mainly include electrolysis, ion exchange, distillation, reverse osmosis and the like. Among them, reverse osmosis and distillation are the most widely used.

[0003] As a key component of reverse osmosis method, reverse osmosis membrane plays an important role in seawater desalination. With the continuous development of production technology, the production of reverse osmosis membrane and its assembly has been quite mature: the production cost of a single product is reduced, the membrane desalination rate is as high as 99.3%, but the relatively short service life of the membrane still makes the cost of seawater desalination high. The average service life of the membrane is less than 5 years, and the pollution of impurities in seawater to the membrane is the main reason for the short service life of the membrane.

[0004] Backwashing of reverse osmosis membrane can greatly improve the service life of the membrane. However, the existing reverse osmosis water purifier with backwashing function has a complex structure, large occupied area, high cost and low running efficiency. In addition, due to the pollution source of the membrane being inside the filter cartridge which is difficult to clean, the backwashing efficiency is low, and the service life of the membrane is not significantly improved. SUMMARY

[0005] The main purpose of the present application is to provide a periodic backwashing seawater reverse osmosis desalination device and method. The device has a compact structure, high running efficiency, and can complete two backwashings and fresh water collection in one cycle; the service efficiency and service life of the reverse osmosis membrane assembly are improved.

[0006] The technical scheme adopted by the present application is:

[0007] A periodic backwash seawater reverse osmosis desalination device, comprising a shell, a filter core assembly, a piston assembly, an inclined disc and a driving device; the inside of the shell is sequentially divided into a seawater layer, a piston layer and a fresh water layer from top to bottom, the upper part of the shell of the seawater layer is provided with a seawater inlet, the lower part of the shell of the seawater layer is provided with a sewage outlet, and the lower part of the shell of the fresh water layer is provided with a fresh water outlet; a plurality of groups of filter core assemblies are arranged in the seawater layer in a ring array, each group of filter core assemblies comprises a filter core inner cylinder and a reverse osmosis membrane wrapped on the surface of the filter core inner cylinder, the filter core inner cylinder is provided with a discharge hole and is hollow inside; a plurality of groups of piston assemblies are arranged in the piston layer in a ring array and are correspondingly arranged below the filter core assemblies, each group of piston assemblies comprises a piston main body and a piston outer cylinder, the upper end of the piston outer cylinder is connected with the filter core inner cylinder of the filter core assembly above it, the upper end of the piston main body is slidingly and sealingly connected with the piston outer cylinder, an internal passage is arranged in the piston main body in the axial direction, and an electromagnetic valve for controlling the opening and closing of the internal passage is arranged, and the middle part of the outer surface of the piston outer cylinder is provided with an electromagnetic device, when the piston main body moves to a position matched with the electromagnetic device, the electromagnetic valve is opened, so that the fresh water in the piston outer cylinder falls to the fresh water layer through the internal passage; the inclined disc is installed below the piston assembly, one side of the inclined disc is higher than the other side, and a ring-shaped track is arranged on the periphery of the inclined disc, and the lower end of the piston main body is arranged in the ring-shaped track and is slidingly connected with the ring-shaped track; the driving device is used for driving the inclined disc to rotate around a vertical center axis, and the inclined disc drives each piston main body to complete a reciprocating motion once per revolution, so as to realize twice backwash and twice fresh water collection.

[0008] In the above scheme, the electromagnetic valve comprises a lock core, a spring and an electromagnetic valve cover, the spring is arranged perpendicular to the internal passage of the piston main body, the outer end of the spring is connected with the electromagnetic valve cover, the inner end of the spring is connected with the lock core, and the lock core can reciprocate in the horizontal direction; the electromagnetic device is an electromagnet installed on the piston outer cylinder; when the piston main body moves to a position matched with the electromagnet, the lock core moves outward under the action of the electromagnet, so that the internal passage of the piston main body is in a connected state; when the piston main body moves to other positions, the lock core moves inward under the action of the spring restoring force, so that the internal passage of the piston main body is in a blocked state.

[0009] In the above scheme, the lower end of the piston main body is designed as a spherical shape to adapt to the ring-shaped track; the bottom of the ring-shaped track is hollowed out to facilitate the falling of fresh water.

[0010] In the above scheme, the filter core assembly further comprises a grid on the surface of the reverse osmosis membrane, and the reverse osmosis membrane is attached to the inside of the grid.

[0011] In the scheme, the driving device comprises a gear box arranged below the inclined disc and a motor arranged outside the shell, the gear box is internally provided with a pair of bevel gears, the output shaft of the motor is connected with the vertical central shaft at the lower part of the inclined disc through the bevel gears, and the motor drives the inclined disc to rotate around the vertical central shaft.

[0012] In the scheme, when the inclined disc rotates to the lowest position of the annular track, the piston body runs to the bottom end of the piston outer cylinder; when the inclined disc rotates to the highest position of the annular track, the piston body runs to the top end of the piston outer cylinder.

[0013] In the scheme, the working process of each filter core assembly in a cycle is as follows:

[0014] a) the piston body is located at the lowest position of the inclined disc, at this time, the inclined disc rotates, the piston body moves upward to pressurize the fresh water in the filter core assembly, until the pressure is greater than that of the seawater side, the fresh water in the filter core assembly flows to the seawater side, and the impurities attached to the surface of the filter core assembly are washed, completing a backwashing;

[0015] b) the piston body runs to the middle height of the inclined disc, at this time, the electromagnetic valve in the piston body contacts with the electromagnetic device of the piston outer cylinder, the electromagnetic valve is opened, the fresh water in the filter core assembly flows out from the channel in the piston body, and a water discharge is completed;

[0016] c) during the process that the piston body runs to the highest position of the inclined disc, the electromagnetic valve in the piston body is separated from the electromagnetic device, the electromagnetic valve is closed, at this time, the piston body compresses the fresh water in the filter core assembly, until the pressure of the fresh water is greater than that of the seawater side, and a second backwashing is completed;

[0017] d) the piston body starts to run from the highest position of the inclined disc to the middle part of the inclined disc, at this time, the piston body descends, the pressurized seawater accelerates to reverse osmosis in the filter core assembly, the electromagnetic valve of the piston body is opened again to start water discharge when the piston body runs to the middle part of the inclined disc, and a second water discharge is completed;

[0018] e) the piston body returns to the initial lowest position from the middle part of the inclined disc, the piston body continues to descend, the pressurized seawater accelerates to reverse osmosis in the filter core assembly and fills the filter core assembly again, and thus a working cycle is completed.

[0019] Correspondingly, the application also provides a method for the periodic backwashing seawater reverse osmosis desalination device, comprising the following steps:

[0020] S1, the seawater to be purified enters the seawater layer of the shell from the seawater inlet, under the action of the pressure difference between the seawater and the filter core assembly, the seawater uniformly enters the filter core assembly from outside to inside;

[0021] S2, start the driving device to drive the inclined disc to rotate, and start the electromagnetic device located at the outer cylinder of the piston, due to the periodic height change caused by the inclination angle of the inclined disc, drive each piston body to reciprocate up and down, and periodically complete the water discharge and backwashing process during the reciprocating movement of the piston.

[0022] In S1 of the above method, seawater is externally pressurized to increase the permeation speed.

[0023] The beneficial effects of the present application are:

[0024] 1. The present application uses a multi-axis parallel structure, sets multiple piston assemblies corresponding to the filter core assemblies, cooperates with the inclined disc, can realize the reciprocating movement of multiple piston bodies in one rotation period, respectively realizes twice freshwater collection, increases the purification amount, and makes the device work continuously and uninterruptedly, thereby improving the seawater desalination efficiency, ensuring the output per unit time and total output. At the same time, through the cooperation of the electromagnetic valve in the piston body and the electromagnetic device of the outer cylinder of the piston, each filter core assembly can realize twice water discharge and twice backwashing process in one period, not only can discharge fresh water in time during the reciprocating movement of the piston, shorten the unit working time of the device, improve the working efficiency, but also realize the integration of seawater desalination and reverse osmosis membrane cleaning, effectively improve the desalination efficiency and prolong the service life of the reverse osmosis membrane.

[0025] 2. The reverse osmosis membrane of the present application is coated on the outer cylinder of the filter core, the fresh water is discharged from the inside of the filter core inner cylinder, and the impurities are blocked outside the cylinder. The membrane assembly is more suitable for backwashing and cleaning, and the impurities are easily discharged from the blowdown port during backwashing, so that the cleaning efficiency is greatly improved.

[0026] 3. The device of the present application has simple and compact structure, is conducive to long-term stable operation of the device, and has small floor area and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 is a perspective structural schematic view of the periodic backwashing seawater reverse osmosis desalination device of the present application;

[0029] Figure 2 is a schematic view of the internal structure of the periodic backwashing seawater reverse osmosis desalination device of the present application;

[0030] Figure 3is a structural schematic diagram of a piston body filter core assembly;

[0031] Figure 4 is a structural schematic diagram of a piston body;

[0032] Figure 5 is the working flow of each filter core assembly in a cycle.

[0033] In the figure: 10, shell; 11, seawater layer; 111, seawater inlet; 112, sewage outlet; 12, piston layer; 13, fresh water layer; 131, fresh water outlet; 14, upper cover;

[0034] 20, filter core assembly; 21, filter core inner cylinder; 22, reverse osmosis membrane; 23, grid;

[0035] 30, piston assembly; 31, piston body; 311, internal passage; 312, lock core; 313, spring; 314, electromagnetic valve cover; 32, piston outer cylinder; 321, electromagnet;

[0036] 40, inclined disc;

[0037] 50, driving device; 51, motor; 52, gear box. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0039] It should be noted that the diagrams provided in the embodiments of the present application only illustrate the basic concept of the present application in a schematic manner, and therefore only the components related to the present application are shown in the diagrams, not the number, shape and size of the components when actually implemented. The actual implementation of each component may be a random change in shape, number and proportion, and the layout pattern of the components may also be more complex.

[0040] In the present application, it should also be noted that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like appear, the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, if the terms "first" and "second" appear, they are only for description and distinction purposes, and cannot be understood as indicating or implying relative importance.

[0041] As Figures 1-2As shown, a periodic backwash seawater reverse osmosis desalination device comprises a shell 10, a filter core assembly 20, a piston assembly 30, an inclined disc 40 and a driving device 50.

[0042] The inside of the shell 10 is divided into a seawater layer 11, a piston layer 12 and a fresh water layer 13 from top to bottom. The upper part of the shell 10 of the seawater layer 11 is provided with a seawater inlet 111, the lower part of the shell 10 of the seawater layer 11 is provided with a sewage outlet 112, and the lower part of the shell 10 of the fresh water layer 13 is provided with a fresh water outlet 131. The seawater to be desalinated enters the seawater layer 11 of the shell 10 from the seawater inlet 111, the impurities after backwashing are discharged through the sewage outlet 112, and the desalinated fresh water is discharged from the fresh water outlet 131. The upper end of the shell 10 is provided with an upper cover 14.

[0043] A plurality of filter core assemblies 20 are arranged in a ring array in the seawater layer 11, as shown in the figure. Figure 3 Each filter core assembly 20 comprises a filter core inner cylinder 21, a reverse osmosis membrane 22 and a grid 23 arranged in sequence from inside to outside. The filter core inner cylinder 21 is provided with a discharge hole and is hollow inside. During installation, the reverse osmosis membrane 22 is attached to the inside of the grid 23, and then the filter core inner cylinder 21 is placed into the grid 23. The filter core inner cylinder 21 plays a flow guiding role while preventing the reverse osmosis membrane 22 and the grid 23 from separating. The grid 23 serves to avoid direct contact between the reverse osmosis membrane 22 and the external seawater environment. Preferably, the reverse osmosis membrane 22 is made of aromatic polyamide membrane with good pressure resistance and chemical stability. The multi-layer structure design of the filter core assembly 20 can make the distribution of seawater more uniform when the seawater passes through the filter core and enters its inside, and the filtering effect is more complete, thereby improving the purity of seawater purification.

[0044] A plurality of piston assemblies 30 are arranged in a ring array in the piston layer 12 and correspond to the plurality of filter core assemblies 20 one by one. Each piston assembly 30 comprises a piston main body 31 and a piston outer cylinder 32. The upper end of the piston outer cylinder 32 is in communication with the filter core inner cylinder 21 of the filter core assembly 20 above it. The upper end of the piston main body 31 is in sliding and sealing connection with the piston outer cylinder 32. The inside of the piston main body 31 is provided with an internal passage 311 in the axial direction and an electromagnetic valve for controlling the opening and closing of the internal passage 311. The middle part of the outer surface of the piston outer cylinder 32 is provided with an electromagnetic device. When the piston main body 31 moves to a position where the electromagnetic valve matches the electromagnetic device, the electromagnetic valve is opened, and the fresh water in the piston outer cylinder 32 falls to the fresh water layer 13 through the internal passage 311. When the piston main body 31 moves to other positions, the electromagnetic valve is closed, and the internal passage 311 is blocked.

[0045] As shown in the figure, Figure 4As shown, the electromagnetic valve comprises a lock core 312, a spring 313 arranged perpendicularly to the internal passage 311 of the piston body 31, and an electromagnetic valve cover 314 connected to the outer end of the spring 313, the inner end of the spring 313 being connected to the lock core 312, the lock core 312 being capable of reciprocating in the horizontal direction; the electromagnetic device is an electromagnet 321 installed on the piston outer cylinder 32; when the piston body 31 moves to the position where the lock core 312 matches the electromagnet 321, the lock core 312 moves outward under the action of the electromagnet 321, so that the internal passage 311 of the piston body 31 is in a communication state; when the piston body 31 moves to other positions, the lock core 312 moves inward under the action of the restoring force of the spring 313, so that the internal passage 311 of the piston body 31 is in a blocked state.

[0046] The inclined disc 40 is installed below the piston assembly 30, one side of the inclined disc 40 is higher and the other side is lower, and an annular track is arranged in the circumferential direction, and the lower end of the piston body 31 is respectively arranged in the annular track and is in sliding connection with the annular track. The lower end of the piston body 31 is designed in a spherical shape to adapt to the annular track; the bottom of the annular track is hollowed out to facilitate the falling of fresh water. The driving device 50 is used to drive the inclined disc 40 to rotate around the vertical central shaft, and the inclined disc 40 drives each piston body 31 to complete a reciprocating motion once per revolution. When the inclined disc 40 rotates to the position where the lower end of the piston body 31 is located at the lowest part of the annular track, the piston body 31 moves to the bottom end of the piston outer cylinder 32; when the inclined disc 40 rotates to the position where the lower end of the piston body 31 is located at the highest part of the annular track, the piston body 31 moves to the top end of the piston outer cylinder 32.

[0047] The driving device 50 comprises a gear box 52 arranged below the inclined disc 40, and a motor 51 arranged outside the shell 10, a pair of bevel gears are built in the gear box 52, the output shaft of the motor 51 and the vertical central shaft of the lower part of the inclined disc 40 are connected through the bevel gears, and the inclined disc 40 is driven to rotate around the vertical central shaft through the motor 51.

[0048] As shown in the figure, Figure 5 The working process of each filter core assembly 20 in a cycle is as follows (according to the initial position of the piston body 31 being located at the lowest part of the inclined disc 40):

[0049] a) The piston body 31 is located at the lowest part of the inclined disc 40, the osmotic pressure of the seawater outside is much greater than that of the desalinated seawater inside, at this time the inclined disc 40 rotates, the piston body 31 moves upward to pressurize the fresh water in the filter core assembly 20, until the pressure is increased to be greater than that of the seawater side, the fresh water in the filter core assembly 20 will flow to the seawater side, and the impurities such as insoluble salts attached to the surface of the filter core assembly 20 are washed, and a backwashing is completed;

[0050] b) Piston body 31 runs to the middle height of the inclined disc 40, at this time the electromagnetic valve inside the piston body 31 contacts the electromagnetic device of the piston outer cylinder 32, the electromagnetic valve opens, due to the seawater pressurization and the pressure release of the fresh water compression at the beginning, the fresh water inside the filter element assembly 20 flows out from the channel 311 inside the piston body 31, this process lasts for a short time, and completes the water release once;

[0051] c) During the process of the piston body 31 running to the highest point of the inclined disc 40, the electromagnetic valve inside the piston body 31 is out of contact with the electromagnetic device, and the electromagnetic valve is closed, at this time the piston body 31 compresses the fresh water in the filter element assembly 20, due to the fact that the internal fresh water pressure is small after the water release operation just completed, the pressurized seawater will first enter the filter element assembly 20 until the fresh water pressure is greater than the seawater side due to the compression of the piston body 31, completing the second backwash;

[0052] d) The piston body 31 starts to run from the highest point of the inclined disc 40 to the middle of the inclined disc 40 again, at this time the piston body 31 is lowered, the pressurized seawater accelerates the reverse osmosis to the inside of the filter element assembly 20, and the electromagnetic valve of the piston body 31 is opened again to start the water release when running to the middle of the inclined disc 40, completing the second water release;

[0053] e) The piston body 31 reverts from the middle of the inclined disc 40 to the initial lowest point, the piston body 31 continues to descend, the pressurized seawater accelerates the reverse osmosis to the inside of the filter element assembly 20 and re-fills the filter element assembly 20, thus completing a working cycle.

[0054] Correspondingly, the application also proposes a method for the above-mentioned periodic backwash seawater reverse osmosis desalination device, comprising the following steps:

[0055] The seawater to be purified enters the seawater layer 11 of the shell 10 from the seawater inlet 111, and under the action of the pressure difference between the seawater and the inside of the filter element assembly 20, the seawater will enter the filter element assembly 20 uniformly from the outside to the inside. The seawater needs to be externally pressurized to improve the permeation speed, and waits for several minutes until the filter element assembly 20 is filled with desalinated seawater.

[0056] The motor 51 of the driving device 50 is started to drive the inclined disc 40 to rotate, and at the same time the electromagnetic device located at the piston outer cylinder 32 is started, due to the periodic change of height caused by the inclination angle of the inclined disc 40, each piston body 31 is driven to move up and down reciprocatingly, and the processes of water release and backwash are periodically completed in the reciprocating movement of the piston.

[0057] It should be noted that according to the needs of implementation, each step / component described in the present application can be split into more steps / components, or two or more steps / components or part of the operation of the steps / components can be combined into a new step / component, to achieve the purpose of the present application.

[0058] The size of the serial number of each step in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0059] It should be understood that those of ordinary skill in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A cyclic back-flushed sea water reverse osmosis desalination unit, characterized in that, The application relates to a filter device, which comprises a shell, a filter core assembly, a piston assembly, an inclined disc and a driving device. The inside of the shell is sequentially divided into a seawater layer, a piston layer and a fresh water layer from top to bottom; the upper part of the shell of the seawater layer is provided with a seawater inlet, and the lower part of the shell of the seawater layer is provided with a sewage outlet; and the lower part of the shell of the fresh water layer is provided with a fresh water outlet. A plurality of groups of the filter core assemblies are arranged in a ring array in the seawater layer; each group of the filter core assemblies comprises a filter core inner cylinder and a reverse osmosis membrane wrapped on the surface of the filter core inner cylinder; the filter core inner cylinder is provided with a discharge hole and is hollow inside; a plurality of groups of the piston assemblies are arranged in a ring array in the piston layer and are correspondingly arranged below the filter core assemblies; each group of the piston assemblies comprises a piston main body and a piston outer cylinder; the upper end of the piston outer cylinder is connected with the filter core inner cylinder of the filter core assembly arranged above the piston outer cylinder; the upper end of the piston main body is slidingly and sealingly connected with the piston outer cylinder; the inside of the piston main body is provided with an internal passage in the axial direction and is provided with an electromagnetic valve for controlling the opening and closing of the internal passage; and the middle part of the outer surface of the piston outer cylinder is provided with an electromagnetic device; when the piston main body moves to a position matched with the electromagnetic device, the electromagnetic valve is opened, so that fresh water in the piston outer cylinder falls to the fresh water layer through the internal passage. The inclined disc is arranged below the piston assembly; the inclined disc is high on one side and low on the other side and is provided with a ring-shaped track in the circumferential direction; the lower end of the piston main body is arranged in the ring-shaped track and is slidingly connected with the ring-shaped track; and the driving device is used for driving the inclined disc to rotate around a vertical central shaft; the inclined disc drives each piston main body to complete a reciprocating motion once per rotation, so that twice reverse flushing and twice fresh water collection are realized.

2. A cyclically back-flushed seawater reverse osmosis desalination apparatus as claimed in claim 1, wherein, The electromagnetic valve comprises a lock core, a spring and an electromagnetic valve cover; the spring is arranged perpendicularly to the internal passage of the piston main body; the outer end of the spring is connected with the electromagnetic valve cover; the inner end of the spring is connected with the lock core; the lock core can reciprocate in the horizontal direction; the electromagnetic device is an electromagnet arranged on the piston outer cylinder; when the piston main body moves to a position matched with the electromagnet, the lock core moves outward under the action of the electromagnet, so that the internal passage of the piston main body is in a connected state; when the piston main body moves to other positions, the lock core moves inward under the action of the restoring force of the spring, so that the internal passage of the piston main body is in a blocked state.

3. The cyclic back-flushed seawater reverse osmosis desalination device of claim 1, wherein, The lower end of the piston main body is designed as a spherical shape to adapt to the ring-shaped track; and the bottom of the ring-shaped track is hollowed out to facilitate the falling of fresh water.

4. The cyclically back-flushed seawater reverse osmosis desalination apparatus of claim 1, wherein, The filter core assembly further comprises a grid arranged on the surface of the reverse osmosis membrane; and the reverse osmosis membrane is arranged inside the grid.

5. The cyclically back-flushed seawater reverse osmosis desalination device of claim 1, wherein, The driving device comprises a gear box arranged below the inclined disc and a motor arranged outside the shell; the gear box is built-in a pair of bevel gears; the output shaft of the motor is connected with the vertical central shaft at the lower part of the inclined disc through the bevel gears; and the motor is used for driving the inclined disc to rotate around the vertical central shaft.

6. The cyclically back-flushed seawater reverse osmosis desalination device of claim 1, wherein, When the inclined disc rotates to a position where the lower end of the piston main body is located at the lowest part of the ring-shaped track, the piston main body moves to the bottom end of the piston outer cylinder; and when the inclined disc rotates to a position where the lower end of the piston main body is located at the highest part of the ring-shaped track, the piston main body moves to the top end of the piston outer cylinder.

7. The cyclically back-flushed seawater reverse osmosis desalination device of claim 1, wherein, The working process of each filter core assembly in a cycle is as follows: a) the piston body is at the lowest point of the inclined disc, at this time the inclined disc rotates, the piston body moves upward to pressurize the fresh water in the filter element assembly, until the pressure is greater than the seawater side, the fresh water in the filter element assembly will flow to the seawater side, and the impurities attached to the surface of the filter element assembly are washed, completing a backwash; b) the piston body runs to the middle height of the inclined disc, at this time the electromagnetic valve in the piston body contacts the electromagnetic device outside the piston cylinder, the electromagnetic valve opens, the fresh water in the filter element assembly flows out from the channel inside the piston body, completing a water release; c) during the process of the piston body running to the highest point of the inclined disc, the electromagnetic valve inside the piston body is out of contact with the electromagnetic device, the electromagnetic valve is closed, at this time the piston body compresses the fresh water in the filter element assembly, until the fresh water pressure is greater than the seawater side, completing the second backwash; d) the piston body starts to run from the highest point of the inclined disc to the middle of the inclined disc, at this time the piston body descends, the pressurized seawater accelerates the reverse osmosis to the inside of the filter element assembly, and when the piston body runs to the middle of the inclined disc, the electromagnetic valve is opened again to start water release, completing the second water release; e) the piston body returns to the initial lowest point from the middle of the inclined disc, the piston body continues to descend, the pressurized seawater accelerates the reverse osmosis to the inside of the filter element assembly and fills the filter element assembly again, thus completing a working cycle.

8. A cyclic back-flushed seawater reverse osmosis desalination process, characterized in that, The periodic backwash seawater reverse osmosis desalination device of claim 1 comprises the following steps: S1, the seawater to be purified enters the seawater layer of the shell from the seawater inlet, under the action of the pressure difference between the seawater and the inside of the filter element assembly, the seawater will uniformly enter the filter element assembly from the outside to the inside; S2, start the driving device to drive the inclined disc to rotate, at the same time start the electromagnetic device located in the piston cylinder, due to the periodic change of height caused by the inclination angle of the inclined disc, drive each piston body to move up and down reciprocatingly, and periodically complete the water release and backwash process during the reciprocating movement of the piston.

9. The cyclic back-flushed seawater reverse osmosis desalination method according to claim 8, characterized in that, In S1, the seawater is pressurized externally to increase the permeation speed.

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